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Genetics > multifactorial > Flashcards

multifactorial Flashcards

exam 1

1
Q

distinct variant of a phenotype characteristics that may be inherited

A

trait

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2
Q

results from the influence of only one gene

A

monogenic trait

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3
Q

results from the combined influence of multiple genes

A

polygenic trait

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4
Q

results from the combined influence of multiple genes and environmental factors

A

multifactorial trait

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5
Q

combined contribution of genes and environmental factors in the causation of a particular disease or trait

A

multifactorial inheritance

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6
Q

(2) multifactorial traits

A

(1) Quantitative

(2) threshold

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7
Q

continuous range of measurement, numerical scale, follows a normal or bell-shaped distribution in populations

A

Quantitative

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8
Q

examples of quantitative traits

A

height, weight, blood pressure, intelligence

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9
Q

trait is either present or absent

A

threshold

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10
Q

liability follows a bell-shaped distribution, and those individuals exceeding the threshold on the liability scale will express the trait

A

threshold

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11
Q

examples of threshold traits

A

club foot, diabetes, cleft lip and palate, pyloric stenosis

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12
Q

total genetic and environmental factors that contribute to development of a trait

A

liability

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13
Q

amount of liability required to exhibit the trait

A

threshold

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14
Q

true or false: liability may be different for males and females

A

true

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15
Q

m?f for cleft lip and palate

A

m>f

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16
Q

m?f for congenital hip dysplasia

A

f>m

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17
Q

m?f for pyloric stenosis

A

m>f

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18
Q

m?f for autism

A

m>f

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19
Q

signs of multifactorial inheritance (4)

A

(1) familial concentration of a disease or trait without a clear mendelian pattern of inheritance
(2) absence of clear biochemical defects resulting from a single abnormal gene
(3) considerable variation in severity and expression of the phenotype
(4) gender difference in the frequency of occurrence

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20
Q

____ ____ are less clear in multifactorial traits than for those that follow mendelian inheritance

A

recurrence risks

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21
Q

_____ is obtained by observation in family or population studies

A

data

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22
Q

5 recurrence risk rules

A
  1. the greater the severity of the proband, the greater the recurrence risk
  2. recurrence risk is greater if the proband is of the less commonly affected sex
  3. recurrence risk is higher if more than one family is affected
  4. recurrence risk decreases rapidly in more distantly related individuals
  5. recurrence risk for first degree relatives is approx. the square root of the population incidence of the trait
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23
Q

true or false:

the lesser the severity, the higher the recurrence risk

A

false–> higher severity, higher risk

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24
Q

is the trait due to genes, environment, or both?

A

estimate heritability

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25
Q

can we locate the causal genes for this trait?

A

perform linkage analysis ‘family studies’

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26
Q

can we identify the specific risk alleles for this trait?

A

perform association studies “ population-based studies”

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27
Q

measure of the proportion of the total phenotypic variance of a trait in a population that is due to genetics

A

heritability

28
Q

the value of heritability is always a fraction between ___ and ___

A

between 0 and 1

29
Q

h2 of 1= entirely genetic –> phenotypic variance=

A

genetic variance

30
Q

estimated from the incidence of a trait among relatives of a known degree of relatdness

A

heritability

31
Q

twin studies, observations of familial aggregation

A

heritability

32
Q

heritability of a trait is estimated from concordance rates for monozygotic versus dizygotic twins

A

twin studies

33
Q

Monozygotic twins share ____% of their genetic information while dizygotic twins share ___% of their genetic information

A

100% MZ

50% DZ

34
Q

true or false: if DZ twins share a trait more often than MZ twins, then this suggests that the trait is influenced by genetic factors

A

false, if DZ share a trait more than it is influenced y genetics

35
Q

used to determine whether the inheritance of a genetic marker is associated with a particular disease/ trait in a family

A

linkage analysis

36
Q

goal for linkage analysis

A

to identify a region of the genome which cosegregates with the disease

37
Q

historically, it was used to identify genetic regions where a ____ _____ gene could be found

A

candidate disease

38
Q

most effective for regions with a _____ ____. Less effective in locating regions which play a role in _____ _____

A

large effect and less effective in multifactorial traits

39
Q

two genetic markers are located close enough together on a chromosome to be inherited together. a recombination is even is unlikely to occur between them

40
Q

a statistical measure of how likely it is for two genetic marker to be linked. based on recombination frequency

41
Q

LOD>3

A

statistically significant evidence of linkage

42
Q

LOD

A

statistically significant evidence against linkage

43
Q

goal of association studies

A

to identify marker alleles for a particular disease/trait within an already designated region or across the genome

44
Q

based on the hypothesis that a particular allele occurs more frequently in individuals with the disease than in controls

A

association studies s

45
Q

uses SNPs

A

association studies

46
Q

___ ___ ___ changes in the DNA which occur throughout the genome

A

single base pair

47
Q

association studies can identify genes with a ___ ____ ___ which may play a role multi factorial disease

A

small overall effect

48
Q

(2) limitations of association studies

A

(1) association of a SNP allele with a phenotype does not prove that once causes the other(correlation does not equal causation)
(2) a larger number of markers are needed because the marker allele needs to be closely linked to the disease locus

49
Q

GWAS

A

genome wide association studies

50
Q

variant with ____ frequency in cases than controls in GWAS

51
Q

true or false: risk of developing Alzheimer’s disease doubles in individuals with an affected first degree relative

A

Alzheimer’s disease

52
Q

which apolipoprotein has been studied extensively as a risk factor in Alzheimer’s disease

53
Q

follows a bell-shaped curve in the general population

54
Q

fragile x syndrome follows which type of inheritance?

A

non-mendelian

55
Q

Cleft palate follows which type of inheritance

56
Q

marfan follows which type of inheritance?

57
Q

height follows which type of inheritance?

A

quantitative

58
Q

who has higher liability for a condition that is more common in males and has the condition?

  • female
  • male
59
Q

multifactorials traits > or < 100% concordance of monozygotic twin

60
Q

dizygotic concordance is > or < than monozygotic concordance

61
Q

limitations with GWAS

A

reproducibility

62
Q

population based study

63
Q

Family based study

A

Linkage analysis

64
Q

In general, the recurrence risk for most isolated birth defects is approximately ____

65
Q

Concordance rate = (formula_

A

Concordance rate= # of all concordant pairs / # of all twin pairs

66
Q

Heritability (h^2) = (formula)

A

H^2= (MZ concordance - DZ concordance) x 2

67
Q

If a trait has 100% genetic concordance MZ=_ and DZ=+,

A

MZ=1 and DZ=0.5

Genetics (7 decks)

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